The purpose of this proposal is to further investigate the proteins which are found in the polyoma virion and to determine their respective role(s) in viral infection, virion assembly and cell transformation. The unique aspects of our proposed investigation include: I. The location and affinity of the various polypeptides associated with the DNA and capsid shell will be determined by in vitro disassembly and reassembly of virions. Optimum physiological conditions will be determined for the EGTA-DTT (chelation of virion associated Ca ion) dissociation of virions. Dissociation products (core complex and capsomeres) will be biophysically characterized, and protein composition, post-translational modification(s) and Ca ion binding site(s) determined. These virion dissociation products will then be used for the in vitro assembly of polyoma virions. II. Identification and isolation of the virion hemagglutinin protein. III. Determination of what effects (i.e., regulatory) the isolated polypeptides and capsomers might have on cellular and viral macromolecular synthesis and on possible involvement in cell transformation. IV. Investigation of the mechanism(s) of intracellular uncoating and the possible involvement of virion polypeptides and histones in the expression of early and late viral functions. V. Temperature sensitive polyoma mutants from appropriate complementation groups will be used to study the virion structure, virion uncoating, virion assembly and regulatory functions of the virion polypeptides.